AlGaN/GaN transistors find their applications in high frequency, high power electronics. Due to their intrinsic properties, i.e. high mobility and high breakdown field, they are suited to serve as amplifiers and switches in telecom and power devices, respectively.
The dispersion, i.e. degradation of the output current under large signal operation at high frequency, is an important problem in AlGaN/GaN transistors. G. Meneghesso, et. al (in IEEE Transactions on Electron Devices, Vol. 51, No. 10, October 2004) report surface states as a cause of the dispersion effect. To avoid or minimize the effect of dispersion, Huili Xing et al. (in IEEE Electron Device Letters, Vol. 25, No. 4, April 2004) installed a field plate on top of the gate.
Another problem is the reverse leakage current of the gate Schottky contact (see Hashizume, T. et al. in Appl. Phys. Lett., vol. 84, pp. 4884-4886, 2004). Hyeongnam Kim et al. (in Appl. Phys. Lett. vol. 86, pp 143505, 2005) showed that a high leakage current leads to losses in the transistor and will influence the reliability.
In EP1612866 a method for manufacturing a group III-nitride field effect device is presented by covering the surface with a thin SiN layer in the same reactor prior to cooling down the structure. Also the corresponding device is presented.
Oxidation of Si3N4 has been reported by Raider, S. I. in J. Electrochem. Soc.: Solid State Science and Technology, April 1976. These oxide states can provide carriers and perform a surface leakage path.